Some last name characters are typically clarified in terms of some or all of their component parts (e.g., radicals). These descriptions can be pretty precise, where a component part(s) is/are only visibly "squeezed", or, e.g., an existing line(s) is/are lengthened, shortened, or moved "a little bit". Some such descriptions take a few more liberties.
I think the first time I was exposed to this clarification of last names was years ago, when I was talking on the phone to a native Chinese speaker, a guy who I had never met. He told me his last name was 張 (Zhāng). Then he added, 弓長張 (gōng cháng Zhāng).
Now, not having known about this common style of clarification of last names, and also not knowing the 弓 (gōng) character, I was pretty confused. Mentally imposing (quite incorrectly) a Western style first-middle-last (e.g., Franklin Delano Roosevelt) structure onto what he had just told me, I asked him if his full name was 張弓長 (Zhāng Gōng Cháng).
If anyone actually is named 張弓長 (Zhāng Gōng Cháng), that would be pretty weird -- it's kind of like someone being named Roose Velt Roosevelt. I think at that point in our conversation, this guy realized I didn't know as much Chinese as he thought I might. When we later met, he may have explained this style of clarification of Chinese characters, but in any case I eventually learned about it.
Both component parts combined without meaningful change:
- 古月胡 gǔ yuè Hú
- 木子李 mù zǐ Lǐ
- 言午許 yán wǔ Xǔ
Both component parts combined with mild changes:
- 耳東陳 ěr dōng Chén (The 耳 character changes this way, but it doesn't always change this way when it's a component of a more complex character.)
- 人可何 rén kě Hé (The 人 character changes this way.)
- 口天吳 kǒu tiān Wú (The 天 character grows "arms".)
- 木易楊 mù yì Yáng (The 易 character gets an additional horizontal line.)
Some characters are identified purely by just specifying a portion of their parts. Within the context of last names, that is sufficient to identify them.
- 草頭黃 cǎo tóu Huáng (The Huáng character that has the 草頭 radical.)
- 雙人徐 shuāng rén Xú (The Xú character that has the 雙人 [double person] radical.)
Somewhere there may be a far more exhaustive compilation of such last name character clarifications. From my own experience, the above are many of the commonly used ones for relatively common last names. Note that last names are simply a subset of characters which can be clarified in this manner.
Some last names are so well-known and common, and other last names having the exact same sound are so rare, that it's unlikely anyone would ask for clarification. A good analogue in English might be Brown. If he calls for take-out, my favorite singer Jackson Browne doesn't likely get asked, "Is that Brown with an e on the end?"
I don't recall ever hearing of this type of clarification for any of:
- 劉 Liú
- 馬 Mǎ
- 王 Wáng (三橫一豎王 sān héng yī shù Wáng, the Wáng character having 3 horizontal strokes and 1 vertical stroke, provided by Yitrun -- thanks!)
The old question, "What's in a name?", has quite a different answer in Chinese!